1. Field of the Invention
The present invention generally relates to optical devices and, more particularly, to optical devices and to monolithic opto-electronic circuits on a semi-insulating substrate.
2. Description of the Prior Art
In recent years a significant amount of research has been directed to develop various devices, utilizing semiconductor materials. Among these devices are optical devices and electronic devices. With modern chip technology very thin layers of semiconductor materials can be grown or deposited on a substrate to produce very small devices. For example, with advances in GaAs device technology heterostructures of GaAs and GaAlAs have been developed to fabricate lasers. Also, due to the high electron mobility in N-type GaAS high speed GaAS electronic devices, such as Gunn oscillators and FET's have been produced. Since optical devices, such as a laser, and electronic devices can be used to form a complex optical circuit, it is highly desirable to be able to integrate all the devices to form a single chip, yet provide the electrical insulation of the devices from one another for proper circuit operation. To date, such complex monolithic integration has not been possible for the following basic reasons. All known GaAs type lasers are fabricated on a conductive GaAs substrate. Likewise, the substrate of known GaAs electronic devices is electrically conductive. Due to such electrical conduction the integration of such devices into a complex monolithic optical circuit i.e. one on a common substrate has not been possible, due to the need to electrically isolate the devices from one another.